Sound perception and auditory scene analysis are thought to be mediated by the ventral auditory pathway, including core auditory cortex, the medial lateral and anterolateral belt regions of auditory cortex, and the ventrolateral prefrontal cortex. The dorsal auditory pathway, in contrast, is thought to mediate spatial and audiomotor behaviors and includes core auditory cortex, the caudolateral and caudomedial belt regions of auditory cortex, and the parietal and frontal cortices. Our current knowledge regarding the roles of these pathways in auditory scene analysis and auditory perception is very limited. The overarching goal of this grant proposal is to identify the systems-level, circuit-level, and lamina specific properties of the auditory brain that contribute to sound perception and auditory scene analysis. To achieve this goal, monkeys will participate in a sound-detection task, which requires them to detect a target tone burst that is embedded within an auditory sequence comprised of other tone bursts. By systematically manipulating the spectral and spatial attributes of the sequence, we change the probability that the monkey can detect the target. This task provides an objective behavioral measure of auditory scene analysis because the target tone burst can only be detected when the sequence is segregated into two auditory streams. While the monkey is participating in this task, neural activity is recorded in one (in Specific Aim #1) or two simultaneously (in Specific Aim #2) brain regions using multi-contact, linear-array electrodes. Electrodes are inserted orthogonal to the cortical laminae to enable us to characterize the laminar distribution of neural activity in each brain region. For each cortical lamina and brain region, we test the correlation between neural activity (i.e., single-unit activit and neural-population responses [e.g., multi-unit activity]) and the monkey's behavioral performance. Specific Aim #1 identifies the neural circuitry in auditory cortex that mediates the integration of spatial information with spectral information to form perceptual representations of an auditory scene. Specific Aim #2 identifies the differential contributions of feedforward versus feedback connections between the prefrontal cortex and the auditory cortex to the neural mechanisms and computations underlying auditory scene analysis. Individually and collectively, the Specific Aims provide valuable, quantitative insights into neural bases of sound perception and auditory scene analysis.